Fire retardant thermoplastic polymer compositions

ABSTRACT

Self-extinguishing, thermoplastic polymer compositions are prepared by the intimate admixture of a thermoplastic polymer with a copolymer of a halogen containing ethylenically unsaturated monomer and a phosphorus containing vinyl monomer, particularly a bis(hydrocarbyl)vinylphosphonate. The thus modified thermoplastic polymers display a high degree of flame retardance without any substantial changes in their physical properties including, for example, their clarity and hardness and the resulting compositions may be safely employed in any application requiring their possible exposure to fire or high temperatures.

This is a division of application Ser. No. 333,595, filed Feb. 20, 1973now U.S. Pat. No. 3,857,906 granted Dec. 31, 1974 which in turn is adivision of application Ser. No. 49,204, filed June 23, 1970, now U.S.Pat. No. 3,725,509 granted Apr. 3, 1973.

BACKGROUND OF THE INVENTION

Many thermoplastic polymers such, for example, as the homo- andcopolymers of methyl methacrylate, polyolefins, polystyrene andacrylonitrile-butadiene-styrene resins are hard and, in many instances,optically clear materials which are widely utilized for the preparationof a broad range of consumer and industrial articles. As normallyprepared, these thermoplastic polymers will ignite and continue to burnupon exposure to flames or high temperatures. However, in manyinstances, particularly where they are being considered for use inbuilding interiors or in applications requiring their prolonged exposureto high temperatures, it is highly desirable that such polymers shoulddisplay fire or flame retardant properties so that they may either meetthe standards set by various building codes or so that they may besafely employed in place of more costly materials.

Prior attempts to provide fire retardant, thermoplastic polymercompositions have involved the use of a variety of extraneous additivessuch, for example, as antimony oxides, halogenated paraffins,halogenated hydrocarbons and low molecular weight phosphate esters.However, the effective utilization of these and other additives hasordinarily required their presence in rather high concentrations whichadversely affected the physical properties of the treated polymers.Thus, the inherent hardness and, in some instances, the clarity of thethermoplastic polymers were particularly prone to deterioration in thepresence of the high concentrations of these additives which werenecessary in order to achieve a self-extinguishing polymer composition.

It is, therefore, the prime object of this invention to provide fireretardant thermoplastic polymer compositions by the use of additiveswhose presence will not adversely affect the inherent physicalproperties such as hardness and, in some instances, the clarity of thethus modified polymers. It is a further object of this invention toprovide a novel class of copolymers which are particularly useful, asadditives, for preparing fire retardant, thermoplastic polymercompositions. Various other objects and advantages of this inventionwill be apparent from the disclosure thereof which follows hereinafter.

TECHNICAL DISCLOSURE OF THE INVENTION

In its broadest aspect, this invention resides in the discovery thatthermoplastic polymers may be rendered fire retardant by theincorporation, thereon, of additives comprising copolymers of: (1) oneor more halogen containing vinyl monomers with (2) one or morephosphorus containing vinyl monomers as hereinafter defined. Moreparticularly, it has now been discovered that the use of copolymers ofone or more halogen containing vinyl monomers with one or morebis(hydrocarbyl) vinylphosphonates provides the thus modified polymerswith a high degree of fire retardance without resulting in any seriousdeleterious effects upon any of their significant physical properties,and particularly their clarity and hardness. Moreover, it is trulysurprising and advantageous to find that the polymer blends resultingfrom the process of this invention display an outstanding degree ofcompatibility since, as is well known to those skilled in the art,physical blends of two or more polymers are almost always characterizedby their inherently poor compatibility.

The novel copolymers suitable for use as fire retardant additives forthermoplastic polymers in the process of this invention comprisecopolymers of:

1. One ore more halogen containing, alpha, beta-ethylenicallyunsaturated, i.e. vinyl, monomers including vinyl halides such, forexample as vinyl chloride, vinyl fluoride and vinyl bromide, halogenatedC₁ -C₁₂ alkyl acrylates and methacrylates such, for example, as methylalpha-chloroacrylate and methyl alpha-bromoacrylate; vinylidene halidessuch, for example, as vinylidene chloride, vinylidene bromide,vinylidene chlorobromide and vinylidene fluoride; halo- substitutednitriles of ethylenically unsaturated carboxylic acids such, forexample, as alpha-chloro-acrylonitrile; and the chlorinated styrenessuch, for example, as alpha-chlorostyrene, o-chlorostyrene,m-chlorostyrene, p-chlorostyrene and 2,4-dichlorostyrene; and

2. one or more bis(hydrocarbyl) vinylphosphonates having the structure:##EQU1## wherein X is selected from the group consisting of hydrogen,halogen, cyano, aryl such as phenyl C₁ -C₁₈ alkyl and ##EQU2## wherein Rand R' are hydrocarbyl and substituted hydrocarbyl groups consistingessentially of hydrogen and carbon containing up to about 18 carbonatoms inclusive with the proviso that R and R' may be the same,different or conjoint, i.e. R and R' may form one single radical.

The use, in this disclosure, of the expression "hydrocarbyl" and"substituted hydrocarbyl groups" refers to the radicals obtained uponthe removal of a hydrogen from a hydrocarbon or substituted hydrocarbongroup which may be either an aliphatic or aromatic group. Thesehydrocarbyl groups may be substituted with any non-interfering groups,i.e. with any group which does not intefere with the polymerization ofthe bis-(hydrocarbyl) vinylphosphonate. Such substituent groups include,for example, chloro, bromo, fluoro, nitro, hydroxy, sulfone, ethoxy,methoxy, nitrile, ether, ester and keto groups and the like.

Illustrative of such aliphatic groups as are represented by R and R' arealkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl,nonyl, pentenyl and hexenyl groups and all of their respective isomers;cycloalkyl groups, such as cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl and cyclohexenyl groups and the like; while typical arylgroups represented by R and R' include phenyl, benzyl, phenethyl, tolyland naphthyl groups and the like.

Representative of the above depicted bis(hydrocarbyl) vinylphosphonatesare:

Bis(beta-chloroethyl) vinylphosphonate;

Bis(beta-chloropropyl) vinylphosphonate;

Bis(beta-chloroethyl) 1-methylvinylphosphonate;

Bis(beta-chloroethyl) 1-cyanovinylphosphonate;

Bis(beta-chloroethyl) 1-chlorovinylphosphonate;

Bis(beta-chloroethyl) 1-phenylvinylphosphonate;

Dimethyl vinylphosphonate;

Diethyl vinylphosphonate;

Bis(omega-chlorobutyl) vinylphosphonate;

Di-n-butyl vinylphosphonate;

Di-isobutyl vinylphosphonate;

Bis(2-chloroisopropyl) 1-methylvinylphosphonate;

Diphenyl vinylphosphonate; and

Bis(2,3-dibromopropyl) vinylphosphonate.

From the above group of bis(hydrocarbyl) vinylphosphonate monomers, itis preferred to employ bis(beta-chloroethyl) vinylphosphonate inpreparing the novel copolymers of this invention since the lattermonomer is a commercially available material and lower in cost than anyof the other bis(hydrocarbyl) vinylphosphonates. It is to be noted, atthis point, that the use of the term "copolymer" in this disclosure ismeant to apply to polymers derived from two, three or more distinctmonomer species.

In addition to the above described bis(hydrocarbyl) vinylphosphonates,it is also possible to prepare copolymers useful as flame retardantadditives for thermoplastic polymers by employing; (1) mono(alkyl) acidvinylphosphonates such, for example, as mono(ethyl) hydrogenvinylphosphonate, mono(butyl) hydrogen vinylphosphonate, mono(octyl)hydrogen vinylphosphonate; mono(beta-chloroethyl) hydrogenvinylphosphonate, mono(omega-chlorooctyl) hydrogen vinylphosphonate; (2)mono(cycloalkyl) and mono(aryl) hydrogen vinylphosphonates such, forexample, as mono(cyclohexyl) hydrogen vinylphosphonate, mono(phenyl)hydrogen vinylphosphonate, mono(benzyl) hydrogen vinylphosphonate; (3)bis(cycloalkyl) and bis(aryl) vinylphosphonate such, for example, asbis(cyclohexyl) vinylphosphonate and bis(benzyl) vinylphosphonates; and,(4) bis(alkyl), bis-(cycloalkyl), and bis(aryl) allylphosphonates such,for example, as bis(beta-chloroethyl) allylphosphonates, bis(cyclohexyl)allylphosphonate and bis(benzyl) allylphosphonate as well as mixtures ofany two or more of the above described phosphonate monomers.

The copolymers of this invention may also, if desired, contain one ormore optional comonomers including alpha-olefins such as ethylene,propylene and butylene; vinyl esters of carboxylic acids such as vinylacetate, vinyl butyrate, and vinyl stearate; the C₁ -C₂₀ alkyl esters ofacrylic and methacrylic acid such as methyl methacrylate, methylacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate andlauryl acrylate; aryl, halo- and nitro- substituted benzyl esters ofacrylic and methacrylic acid such as benzyl acrylate and 2-chlorobenzylacrylate; ethylenically unsaturated monocarboxylic-acids such as acrylicand methacrylic acids; ethylenically unsaturated dicarboxylic acids,their anhydrides and their C₁ -C₂₀ mono- and dialkyl esters such asaconitic acid, fumaric acid, maleic acid, itaconic acid, citraconicacid, maleic anhydride, dibutyl fumarate and monoethyl maleate; amidesof ethylenically unsaturated carboxylic acids such as acrylamide andmethacrylamide; vinyl aryl compounds such as styrene and alpha-methylstyrene; nitriles of ethylenically unsaturated carboxylic acids such asacrylonitrile and methacrylonitrile; C₁ -C₂₀ alkyl vinyl ethers such asmethyl vinyl ether, ethyl vinyl ether and stearyl vinyl ether; dienessuch as isoprene and butadiene; and, glycidyl esters of acrylic andmethacrylic acid such as glycidyl acrylate and glycidyl methacrylate,etc. Preferred for use as optional comonomers are methyl methacrylate,acrylonitrile and methacrylonitrile.

The above described copolymers may be prepared by means of anyconvenient polymerization technique known to those skilled in the artsuch, for example, as by means of a free radical, ionically or Zieglercatalyst initiated bulk, emulsion, solution or suspension typepolymerization technique.

However, for use as flame retardant additives for thermoplasticpolymers, it is preferred that they be prepared by means of a freeradical initiated, suspension polymerization process in an aqueousmedium containing from about 0.01 to 5%, as based on the total weight ofthe monomer mixture, of a suspension agent such, for example, asgelatin, starch, hydroxymethyl cellulose, hydroxyethyl cellulose,hydroxypropyl cellulose, carboxymethyl cellulose, talc, clay, polyvinylalcohol and the like. As a catalyst for the polymerization, one may usefrom about 0.01 to 5.0%, as based on the total weight of the monomermixture, of a monomer soluble azo or peroxide compound such, forexample, as azobisisobutyronitrile, lauroyl peroxide, benzoyl peroxide,isopropylperoxy dicarbonate, t-butyl peroxypivalate and the like.Polymerization may ordinarily be initiated by heating the system to atemperature in the range of from about -10° to 100°C. for a period offrom about 1 to 30 hours with agitation being applied throughout thecourse of the reaction. The resulting product will comprise an aqueoussuspension of the desired copolymers which will be in the form ofparticulate solids having a resin solids content in the range of fromabout 5 to 6%, by weight. These copolymer particles will have a particlesize in the range of from about 2 to 500 microns with a range of fromabout 50 to 250 microns being preferred when these copolymers are to beused as additives for preparing flame retardant, thermoplastic polymers.These copolymers should have a molecular weight, as expressed in termsof their Relative Viscosity, of from about 1.5 to 3.0 when determined,at 25°C. with a 1%, by weight, solution of the copolymer incyclohexanone.

With respect to proportions, these novel copolymers may contain fromabout 2.5 to 99%, by weight, of one or more of the above describedbis(hydrocarbyl) vinylphosphonates with the balance of the copolymercomprising one or more of the above described halogen containing,ethylenically unsaturated monomers together with from 0 to about 50%, byweight of one or more of the above described optional comonomers.Optimum results, as flame retardant additives for thermoplasticpolymers, are obtained by the use of copolymers containing from about2.5 to 60% of one or more bis(hydrocarbyl) vinylphosphonates, preferablybis(beta-chloroethyl) vinylphosphonate.

It is to be noted, with respect to the above described proportions forthe composition of the copolymers of this invention, that it has beenfound that it becomes increasingly more difficult to attain goodpolymerization conversion rates as attempts are made to increase theamount of the bis(hydrocarbyl) vinylphosphonate in the resultingcopolymer substantially above a concentration of about 60%, by weight.On the other hand, the use of these copolymers as flame retardantadditives for thermoplastic polymers becomes progressively moreinefficient when they contain substantially less than about 5%, byweight, of one or more bis(hydrocarbyl) vinylphosphonates since theresulting blend will then require the presence of a rather highconcentration of the copolymer in order to attain flame retardancy. Theuse of such high concentrations of these copolymer additives may, inturn, result in some deterioration in the inherent physical propertiesof the thus modified thermoplastic polymer.

Specific copolymer compositions which have been found to provideparticularly good results as additives for the preparation of fireretardant, thermoplastic polymer composition are:

1. a copolymer of vinyl chloride with about 10 to 40%, by weight, ofbis(beta-chloroethyl) vinylphosphonate, and

2. a terpolymer containing about 10 to 60%, by weight, of vinylchloride, about 10 to 60%, by weight of vinyl bromide; and about 10 to60%, by weight of bis(beta-chloroethyl) vinylphosphonate.

In all cases, the novel copolymers of this invention have been found toprovide blends with thermoplastic polymers which are characterized bytheir outstanding fire retardancy, their excellent compatibility andtheir retention of physical properties such as hardness, tensile andimpact strengths and clarity in those cases where the initial polymersubstrate is itself clear. As used in this disclosure, the term "fireretardant" or "flame retardant" is intended to refer to that particularproperty of a material which provides it with a degree of resistance toignition and burning. Thus, a fire or flame retardant composition is onewhich has a low level of flammability and flame spread. This propertymay be conveniently evaluated by means of any of the standard flameretardancy tests such, for example, as the ASTM test D-635.

In addition to being used as fire retardant additives for thepreparation of thermoplastic polymer compositions, the bis(hydrocarbyl)vinylphosphonate copolymers of this invention may be used in any of thevarious coating, adhesive, laminating impregnating and moldingapplications known to those skilled in the art. Thus, they may be coatedupon and/or absorbed by all types of substrates to which it is desiredto impart fire retardant properties. They may, therefore, be used ascoatings, impregnants, fillers, laminants, and adhesives for suchsubstrates as wood; paper; metals; textiles based on either natural orsynthetic fibers or blends thereof; synethetic polymer films such asthose based upon polyolefins, regenerated cellulose, i.e. cellophane,polyvinyl chloride, polyesters and the like; leather; natural andsynthetic rubber; fiberboard; and synthetic plastics prepared by meansof either addition or condensation polymerization techniques.

Any desired thermoplastic polymers may be blended with the abovedescribed bis(hydrocarbyl) vinylphosphonate copolymers in order toprepare fire retardant compositions. Such thermoplastic polymersinclude:

1. the homopolymer of methyl methacrylate, i.e. polymethyl methacrylate,as well as copolymers of methyl methacrylate with minor proportions ofone or more alpha, beta-ethylenically unsaturated monomers which arepolymerizable therewith including: the C₁ -C₈ alkyl, cycloalkyl andbicycloalkyl esters of acrylic acid and the C₂ -C₈ alkyl, cycloalkyl andbicycloalkyl esters of methacrylic acid such, for example, as ethylacrylate and methacrylate, butyl methacrylate, ethyl-hexyl methacrylate,norbornyl acrylate, and cyclohexyl acrylate; vinyl aryl compounds such,for example, as alpha-methyl styrene and styrene; and, nitriles ofalpha, beta-ethylenically unsaturated carboxylic acids such, forexample, as acrylonitrile and methacrylonitrile. From the above givengroup, the use of the C₁ -C₁₈ aklyl esters of acrylic acid, particularlyethyl acrylate, and of the C₂ -C₈ alkyl esters of methacrylic acid ispreferred.

2. acrylonitrile-butadiene-styrene resins, commonly referred to as "ABS"resins which generally comprise either a mixture of a 60 to 80:40 to 20styrene:acrylonitrile copolymer with from about 10 to 40%, by weight ofa 5 to 40:95 to 60 acrylonitrile:butadiene copolymer or a mixture of a60 to 80:40 to 20 styrene:acrylonitrile copolymer with from about 10 to40%, by weight, of a graft of the latter copolymer onto polybutadiene.

3. poly(alpha-olefins) such as polypropylene and polyethylene andcopolymers of one or more alpha-olefins, such as ethylene or propylene,with a minor proportion of one or more ethylenically unsaturatedmonomers including 4-methyl pentene-1; butene-1; norbornene and itsderivatives; (EPDM) cyclopetadiene; cyclopentene; cyclobutene; vinylacetate; the C₁ -C₁₂ alkyl acrylate and methacrylate esters; as well asblends of the homo- and copolymers of alpha-olefins with other types ofthermoplastic polymers.

4. polystyrene and copolymers of styrene or alpha-methyl styrene with aminor proportion of one or more ethylenically unsaturated comonomerssuch, for example, as nitriles of ethylenically unsaturated carboxylicacids including acrylonitrile and methacrylonitrile; and C₁ -C₁₂ alkylesters of acrylic and methacrylic acid such, for example, as methylmethacrylate and 2-ethyl-hexyl acrylate; and graft copolymers of styreneor alpha-methyl-styrene with polybutadiene and other hydrocarbonelastomers.

5. cellulosic resins including cellulose esters and mixed esters such,for example, as cellulose nitrate, cellulose acetate, cellulosebutyrate, cellulose propionate, cellulose acetate-butyrate, celluloseacetate-propionate and cellulose ethers such, for example, as ethylcellulose;

6. polyamide resins, i.e. the resins made by the condensation of di- orpolyamines with di- or polybasic acids or by polymerization of lactamsor amino acids. Typical polyamides include: nylon 4 which is made frompyrrolidone; nylon 6 obtained by polycondensation of caprolactam; nylon66 obtained by the condensation of hexamethylene diamine with adidicacid; nylon 610 obtained by the condensation of hexamethylenediaminewith sebacic acid; nylon 7 which is a polymer of ethyl aminoheptanoate;nylon 9 made from 9-aminononanoic acid; and nylon 11 made from 11-aminoundecanoic acid;

7.polyester resins, i.e. the resins produced by the condensation ofsaturated or unsaturated dibasic acids, such as terephthalic, maleic,fumeric, isophthalic, adipic and azelaic acids with dihydric alcoholssuch as ethylene glycol, propylene glycol, diethylene glycol anddipropylene glycol. Where the resin is made with an unsaturated acid, apolymerizable monomer such, for example, as styrene, vinyl toluene,diallyl phthalate, methyl methacrylate; chlorostyrene, alpha-methylstyrene, divinyl benzene or triallyl cyanurate is often included in thecomposition:

8. polyurethane resins, i.e. the resins formed by the reaction between abi- or polyfunctional hydroxyl containing compound, such as a polyetheror polyester, and a di- or poly-isocyanate such as toluene disiocyanateor diphenylmethane-4, 4'-diisocyanate;

9.polycarbonate resins, i.e. the resins derived from the reactionbetween a difunctional alcohol or phenol, such as bisphenol A, andphosgene or an alkyl or aryl carbonate;

10. polyacetal resins, i.e. the resins derived from the anionicpolymerization of formaldehyde to obtain a linear molecule of the type--O--CH₂ --O--CH₂ --O--CH₂ --;

11. polyphenylene oxide resins made by the oxidative polymerization of2,6-dimethylphenol in the presence of a copper-amine-complex catalyst;

12. polysulfone resins, i.e. the resins containing in SO₂ linkage asderived from the reaction of sulfur dioxide with olefins such as1-butene or, more preferably, by reaction of bisphenol A with4,4'-dichlorodiphenyl sulfone.

13. the acrylate:styrene:acrylonitrile resins, commonly referred to as"ASA" resins, which comprise a copolymer containing a major proportionof a C₂ -C₈ alkyl acrylate elastomer upon which is grafted about 80-72%of the weight of the latter copolymer of a 70-80:30-20styrene:acrylonitrile copolymer.

In effect, one may utilize any thermoplastic polymer, i.e. any polymerthat may be softened by heat and then regain its original properties oncooling, in preparing the fire retardant compositions of this invention.

The actual blending of the copolymer additives of this invention withthe selected polymeric substrate, i.e. with any one or more of the abovedescribed thermoplastic polymers, may be accomplished by means of anyconvenient procedure which will result in an intimate admixture of theadditive within the mass of the substrate polymer. Thus, for example, anaqueous suspension containing the particles of the copolymer additivemay simply be blended or otherwise admixed with the substrate polymerwhich should, preferably, be in the form of an aqueous latex orsuspension. Or, if desired, the copolymer additive and the thermoplasticpolymer substrate may be admixed while each is in the form of a solidpowder.

The blending operation may also be carried out by means of a procedurein which the thermoplastic polymer which comprises the substrate isitself polymerized while in the presence of an aqueous emulsion orsuspension or organic solvent solution containing one or more of thepreviously polymerized copolymer additives of this invention.Alternatively, the bis-(hydrocarbyl) vinylphosphonate containingcopolymer additive may be polymerized in a system which contains thepreviously polymerized selected thermoplastic polymer substrate in anappropriate physical form, e.g. as an aqueous suspension or emulsion oras an organic solvent solution.

With respect to proportions, the amount of bis(hydrocarbyl)vinylphosphonate containing copolymer which may be admixed with athermoplastic polymer substrate will depend, primarily, upon suchfactors as the particular phosphonate copolymer and thermoplasticpolymer substrate which are to be blended with one another, the degreeof fire retardancy desired in the resulting blend, the degree ofclarity, hardness and other specific physical properties which aresought as well as other technical and economic considerations known andunderstood by those skilled in the art. However, in order to attain acomposition which will be self-extinguishing, it is generally desirableto introduce an effective concentration of the bis(alkyl)vinylphosphonate copolymer additive which will be sufficient to providethe resulting blend with at least about 0.5%, by weight, of phosphorusand with at least about 10%, by weight, of halogen, i.e. chlorine and/orbromine, derived from the halogen containing ethylenically unsaturatedmonomer and also, if possible, from the bis(hydrocarbyl)vinylphosphonate.

The fire retardant, thermoplastic polymer compositions of this inventioncan be prepared so as to contain various optional additives which mayinclude plasticizers such as the alkyl esters of phthalic, adipic andsebacic acids such, for example, as dioctyl phthalate and ditridecylphthalate and aryl phosphate esters such, for example, as diphenyl andtricresyl phosphate, etc.: lubricants and mold release agents such asstearic acid or its metal salts, petroleum based waxes, mineral oils,polyethylene waxes, etc.; and heat and light stabilizers such as barium,cadmium, calcium, zinc soaps or phenates, basic lead compounds,organo-tin compounds, such as dialkyl tin mercaptides and dialkyl tinmalcates, thiolauric anhydride and n-butyl stannoic acid, epoxidizedoils, alkyl diphenyl phosphites, triaryl phosphites, phenyl salicylates,benzophenones and benzotriazoles, etc. For a more complete listing ofplasticizers, lubricants, stabilizers and other functional additives,one may consult "Polyvinyl Chloride" by H. A. Sarvetnick published byVan Nostrand Reinhold Co., New York, N.Y., in 1969.

The compositions of this invention may also contain fillers, pigments,dyes, opacifying agents, decorative additives such as reflective metalfoils or flakes, and other imbedded solid objects such as fiber glass,textile fibers, paper, and the like, provided that they do not detractfrom the flame retardency of these products. In addition, thecompositions may contain other flame retardants such as antimonycomponds, halogenated alkyl phosphates or phosphonates, alkyl acidphosphates, or small concentrations of phosphoric acid.

The novel fire retardant compositions of this invention, comprisingblends of any of the above described thermoplastic polymers with one ormore of the novel fire retardant additives of this invention, may beutilized in any of the coating, impregnating and especially in themolding applications known to those skilled in the art wherein it isdesired to provide fire retardancy to the resulting end product. Forexample, these compositions may be used for preparing such diverse itemsas calendered films, blow molded bottles, extruded flat bed and blownfilms, extruded and shaped articles such as panels, sheets, rods andtubes, etc. and in carrying out such processes as injection molding,fluidized bed coating, electrostatic powder spraying and rotationalcoating, etc. More particularly, those compositions which are opticallyclear such, for example, as those based upon homo- or copolymers ofmethyl methacrylate or homo- or copolymers of styrene may be utilizedfor preparing such articles as lenses, aircraft canopies, windowswindshields, lighting fixtures, and advertising displays. Applicationswherein optical clarity is not essential include such automotiveapplications as seat backs, door panels, instrument panels, head rests,arm rests, package shelves plated hardware, radiator grills, fenderextensions and liners, wheel covers and gas tanks. Non-automotiveapplications include their use as structural and decorative componentsfor both the interiors and exteriors of conventional houses and mobilehomes and as structural and decorative elements of business machines andelectrical appliances.

The following examples will further illustrate the embodiment of thisinvenion. In these examples, all parts given are by weight unlessotherewise noted.

EXAMPLE I

This example illustrates the preparation of a bis (hydrocarbyl)vinylphosphorate copolymer as well as its subsequent use in preparing afire retardant, thermoplastic polymer composition.

Into a 32 ounce reaction vessel, there is charged 38g ofbis(beta-chloroethyl) vinylphosphonate, hereinafter referred to as"bis-beta"; 75 g of a 1% aqueous solution of methyl cellulose; 0.8g of a75% solution of t-butyl peroxypivalate in mineral spirits; and, 375g ofdeionized water. The reaction vessel is chilled to a temperature ofabout 20°C. 112g of vinyl chloride monomer is introduced whereupon thereactor is capped and tumbled end-over-end for 12 hours in a 60°C.constant temperature bath.

The resulting aqueous suspension has a resin solids content of 25%, byweight, of a 75:25vinyl chloride:bis-beta copolymer having an averageparticle size of about 200 microns and a Relative Viscosity of 1.75 asdetermined with a 0.1g/deciliter solution of the copolymer incyclohexanone at 25°C. After filtering and drying, a small portion ofthe copolymer solids is methanol extracted in a Soxhlet apparatus andessentially no free bis-beta is found to have been removed therebyindicating that there is no unreacted bis-beta present in the copolymer.

A total of 44 parts of the above described vinyl chloride:bis-betacopolymer, which is in the form of a dry, particulate mass, isintimately admixed with 56 parts of an 80:20 methyl methacrylate:ethylacetate copolymer and the resulting mixture, which is found to have aphosphorus content of 1.28%, by weight, and a chlorine content of 21.8%,by weight, is thereupon fluxed on two-roll mill operating at atemperature of 165°C. A 0.065 inch thick sheet is then pressed from thefluxed mixture and is found to have excellent color and claritycomparable to that exhibited by a control which comprises a 0.065 inchthick sheet prepared by the identical procedure as described aboveusing, in this instance, an unmodified batch of the same 80:20 methylmethacrylate:ethyl acrylate copolymer.

The fire retardancy of the control sheet and of the sheet prepared fromthenovel composition of this invention is then evaluated using theprocedure of the ASTM D-635 test. In brief, this test involves preparing5 inch × 1/2 inch × 0.05 inch specimens from the respective sheets.These specimens are then suspended so that their 5 inch dimension ishorizontal and their 1/2 inch dimension is inclined at a 45° angle.Oneend of the thus suspended specimen is then contacted, for 30 secondperiods, with a 1 inch high flame from a 3/8 inch diameter barrel bunsenburner fitted with a 17/8 inch wide wing top.

As evaluated by means of the latter test procedure, it is found that thesheet containing the vinyl chloride:bis-beta copolymer additive of thisinvention is completely non-burning whereas the unmodified control burnsat a rate of 1.94 inches per minute until it is entirely consumed.

Comparable results are attained by the use, as fire retardant copolymeradditives, of similarly prepared bis:beta copolymers in which the vinylchloride is replaced, respectively, with alpha- chloroacrylonitrile,alpha-chlorostyrene and methyl alpha-chloroacrylate.

EXAMPLE II

The suspension polymerization procedure described in Example I,hereinabove, is followed in order to prepare the variousbis(hydrocarbyl) vinylphosphonate copolymer additives listedbelow:COPOLYMER NO. COMPOSITION BYWEIGHT______________________________________1 84:16 vinylbromide:bis-beta2 30:50:20 vinyl chloride:vinyl bromide: bis-beta360:20:20 vinyl chloride:vinyl bromide: bis-beta4 82:18 vinylidenechloride:bis-beta______________________________________

Samples of each of the above described copolymer additives are thenintimately admixed with various thermoplastic polymer substrates whichinclude:

    THERMOPLASTIC  DESCRIPTION OF POLYMER                                         POLYMER SUBSTRATE NO.                                                                        SUBSTRATE (BY WEIGHT)                                          __________________________________________________________________________    1              An 80:20 methyl methacrylate:ethyl                                             acrylate copolymer                                            2              An ABS resin sold by Monsanto Chemical                                         Co. under the trademark "Lustran 461"                         3              Polymethyl methacrylate                                        4              A 75:25 styrene:acrylonitrile copolymer                        __________________________________________________________________________

The resulting blends are then used for the preparation of 0.065 inchthick sheets by means of the milling procedure set forth in Example I.The fire retardancy of these sheets, as well as of controls whichcomprise sheets prepared from samples of the various unmodifiedthermoplastic polymer substrates, is then evaluated by means of theprocedure of the ASTM D-635 test. Table I hereinbelow, provides adescription of the composition of the various sheets while Table 2describes the results attained in their fire retardancy evaluation.

                                      TABLE NO. I                                 __________________________________________________________________________    COMPOSITION OF SHEETS UNDERGOING EVALUATION                                       COPOLY-              %, BY WT.                                                MER           THERMO-                                                                              THERMO-     % BY                                         ADDI- % BY WT.                                                                              PLASTIC                                                                              PLASTIC                                                                             % BY WT.                                                                            WT.                                      SHEET                                                                             TIVE  COPOLYMER                                                                             POLYMER                                                                              POLYMER                                                                             PHOS- HALO-                                    NO. NO.   ADDITIVE                                                                              SUBSTR.NO.                                                                           SUBSTR.                                                                             PHORUS                                                                              GEN                                      __________________________________________________________________________    1   1     44      1      66    0.94  29.6                                     2   2     44      1      66    1.17  26.6                                     3   3     50      2      50    1.80  27.6                                     4   3     36      2      64    1.40  18.2                                     5   3     50      3      50    1.33  27.6                                     6   3     50      4      50    1.33  27.6                                     7   4     50      1      50    1.20  32.6                                     1C  --     0      1      100   0     0                                        2C  --     0      2      100   0     0                                        3C  --     0      3      100   0     0                                        4C  --     0      4      100   0     0                                        __________________________________________________________________________

                  TABLE NO. 2                                                     ______________________________________                                        Flame Retardancy Evaluation                                                   Sheet No.                                                                     1        Completely non-burning                                               2        Completely non-burning                                               3        Self-extinguishing as defined by ASTM test D-635                     4        Self-extinguishing as defined by ASTM test D-635                     5        Completely non-burning                                               6        Self-extinguishing as defined by ASTM test D-635                     7        Completely non-burning                                               1C       Burns at rate of 1.94 inches/minute until                                      entirely consumed                                                   2C       Burns at rate of 2.2 inches/minute until                                       entirely consumed                                                   3C       Burns at rate of 2.3 inches/minute until                                       entirely consumed                                                   4C       Burns at rate of 2.3 inches/minute until                                       entirely consumed                                                   ______________________________________                                    

The above given data is clearly indicative of the excellent results thatare achieved in the flameproofing of thermoplastic polymers with thenovelbis(hydrocarbyl) vinylphosphonate copolymer additives of thisinvention in a direct comparison with unmodified control specimens, i.e.sheets numbers1C - 4C, of the identical thermoplastic polymrs with whichthese additives are here blended.

Comparable results, with respect to flame retardancy, are achieved usinga copolymer containing 80 parts by weight of vinyl chloride and 20parts, byweight, respectively of each of the following bis(hydrocarbyl)vinylphosphonate monomers:

bis(beta-chloroethyl) 1-cyanovinylphosphonate,

bis(beta-chloropropyl) vinylphosphonate,

bis(beta-chloroethyl) 1-phenylvinylphosphonate,

di-n-butyl vinylphosphonate and

diphenyl vinylphosphonate;

these copolymers being blended with the following thermoplastic polymersubstrates:

an acrylate:styrene:acrylonitrile resin

polypropylene,

polyethylene,

polyurethane,

polycarbonate,

cellulose acetate,

nylon 66 and

polyphenylene oxide.

Variations may be made in proportions, procedures and materials withoutdeparting from the scope of this invention as defined by the followingclaims.

What is claimed is:
 1. A fire retardant, thermoplastic polymercomposition comprising an intimate admixture of a polyester resin formedby condensation of a dibasic acid with a dihydric alcohol and aneffective concentration to render said polymer composition flameretardant of a copolymer of:1. at least one halogen containing,ethylenically unsaturated monomer selected from the group consisting ofvinyl halides, vinylidene halides, chlorinated styrenes, halogenated C₁-C₁₂ alkyl acrylates, and methacrylates and halo-substituted nitriles ofethylenically unsaturated carboxylic acids; and
 2. from about 2.5 to99%, by weight of at least one bis(hydrocarbyl) vinylphosphonate havingthe structure: ##EQU3## wherein X is selected from the group consistingof hydrogen, halogen, cyano, aryl, C₁ -C₁₈ alkyl and ##EQU4## wherein Rand R' are hydrocarbyl and substituted hydrocarbyl groups which can bethe same, different or conjoint.
 2. The composition of claim 1, whereinthe halogen containing, ethylenically unsaturated monomer of saidcopolymer is a vinyl halide selected from the group consisting of vinylchloride, vinyl fluoride and vinyl bromide.
 3. The composition of claim1, wherein the vinylidene halide of said copolymer is vinylidenechloride.
 4. The composition of claim 1, wherein the halo-substitutednitrile of an ethylenically unsaturated carboxylic acid of saidcopolymer is alpha-chloroacrylonitrile.
 5. The composition of claim 1,wherein said copolymer contains from about 5 to 60%, by weight, of saidbis(hydrocarbyl) vinylphosphonate.
 6. The composition of claim 1,wherein the bis(hydrocarbyl) vinylphosphonate of said copolymer isbis(beta-chloroethyl) vinylphosphonate.
 7. The composition of claim 1,wherein said copolymer is a copolymer of vinyl chloride and from about10 to 40%, by weight, of bis(beta-chloroethyl) vinylphosphonate.
 8. Thecomposition of claim 1, wherein said copolymer is a copolymer of fromabout 10 to 60%, by weight, of vinyl chloride; from about 10 to 60%, byweight, of vinyl bromide; and, from about 10 to 60%, by weight, ofbis(beta-chloroethyl) vinylphosphonate.